WIO > Gravel
Gravel is the middle grade in the WIO range — coarser than the sands, more uniform than the mixed-grain riverbeds. It is the material that goes between the two, and in a river-style scape it is what makes the transition from fine foreground to coarse background look like a real watercourse rather than a line drawn in a tank.
What gravel is actually for in a scape
Natural rivers sort their bed by flow. Fines settle where the water is slow, coarse material sits where it runs fast, and the two grade into one another. Reproducing that grading is the single most effective thing you can do to make a substrate look convincing — more effective than the color of any individual material.
In practice that means sand at the front, gravel through the middle and around the base of stones, and coarser material or riverbed blend at the back. The eye reads the progression as depth and current even though the water in your tank is doing nothing of the sort.
Gravel also does useful work at the foot of hardscape, where it fills the awkward gap between a stone's irregular base and a flat substrate line, and makes the rock look bedded in rather than balanced on top.
Practical advantages over sand
It does not compact. Fine sand in a deep bed can go anaerobic in pockets; gravel stays open, water moves through it, and roots get oxygen. It also does not blow around under flow, so it holds its shape near outflows and powerheads where sand migrates.
And it is far easier to maintain. Debris settles into gravel and can be vacuumed out; on sand it sits on the surface and shows.
What it does not do
It holds no nutrients and provides no buffering. Gravel is inert bulk, not a growing medium. If you are planting into it, use root tabs for heavy root feeders such as swords, crypts and vallisneria, or put an aquasoil layer underneath and cap it with the gravel.
Bumblebee
The current gravel in the range is Bumblebee — the banded light-and-dark family that also appears in WIO's stones, nano stones, boulders and sand. That consistency is the reason to use it: a Bumblebee gravel bed under Bumblebee stone is a scape that looks like one decision, which is most of what separates a good layout from a collection of nice objects.
Sold in 2 kg bags, which suits it to accent and transition work rather than as a whole substrate in a large tank.
Before it goes in
Rinse it. Natural material carries fines, and skipping the rinse buys you a week of cloudy water and a filter full of silt. Rinse in batches in a bucket until the water runs clear, and fill the finished tank slowly onto a plate or a bag so you do not excavate what you just built.
Chemistry
WIO does not publish hardness or pH figures. If you keep Caridina shrimp, wild bettas or anything soft-water, test a pinch with white vinegar first — fizzing means carbonate content that will raise hardness over time, no reaction means inert. For community fish and Neocaridina on San Diego's hard tap water, it makes no practical difference.
Ask us how much you need
Substrate quantities are easy to get wrong in both directions. Tell us your tank dimensions and what you are trying to build and we will work out the amounts across sand, gravel and riverbed before you buy. Both stores test water for free. See the full aquascaping range, or the River Kits if you would rather have the whole thing matched in one box.